1. Field of the Invention
The invention relates in general to a power correction factor (PFC) apparatus, and more particularly to a PFC apparatus with an embedded DC-DC converter.
2. Description of the Related Art
Ordinary display apparatus, such as cathode-ray tube (CRT) display or liquid crystal display (LCD), can only provide an image up to 30–40 inches wide and is not convenient to carry with due to huge size. The projector, which is capable of outputting an image up to tens or hundreds inches wide and is much smaller than that of a CRT display or an LCD, outdoes the CRT display and the LCD in terms of entertainment purpose or business briefing.
FIG. 1 is a block diagram of a projector of prior art. A projector 100 comprises a power factor controller 110, a direct-current to direct-current (DC-DC) conversion circuit 120, a lamp-ignition circuit 130, a control circuit 140, and a lamp 150. The power factor controller 110 and the DC-DC conversion circuit 120 are power suppliers of the projector 100. The power factor controller 110 supplies a high-voltage DC power source of about 380V to the lamp-ignition circuit 130 and a high-voltage DC power source of about 380V of to the DC-DC conversion circuit 120. The lamp-ignition circuit 130, an electronic ballast for instance, is for igniting and providing power to the lamp 150. The DC-DC conversion circuit 120, such as an isolated fly-back circuit, provides a DC power source of 12V, 5V or 3.3V for the control circuit 140 to use. The control circuit 140 is for controlling the operation of the projector 100.
Along with the advance in technology, the projector is also becoming smaller, lighter, slimmer and shorter to give the user a better portability. Therefore, miniaturization has always been an important object for the manufacturer to achieve.